Flashcards in Fish communication Deck (55)
What are the different ways in fish comunicate?
Vision, olfaction, sound, electrosensation, mechanoreception
All the focusing is done by what in fish?
Because the cornea and water have the same refractive index
What is the refractive index?
How much light gets bent.
Where does actual image forming take place?
What are the different layers or cell types in the retina?
At the back is the pigment epithelium, then photoreceptors (rods and cones), then nuclear layer (inner and outer) then ganglion cells whose axons form the optic nerve.
Cones are for what type of vision?
Cones - photopic, bright light and colour - lots of photons
Rods - scotopic vision - dark, low light
Describe the retinomotor adaptation.
Rods are sensitive to light and can get photobleached so, this comes into play.
In the presence of lots of light, the pigment epithelium will migrate down and the rods will migrate up/stretch (stay attached, essentially elongate) to prevent photobleaching and protect the rods from bright light.
When the light is dim, the opposite occurs, pigment layer migrates back up, and rods go back in the path of photons.
What is spherical abberation?
Beams of light at the edges of a sphere will get focused at a different spot then those travelling through the middle of the sphere.
What is chromatic abberration?
same as spherical abberation but with colour.
Colours have different wavelengths and get distorted differently in a perfect sphere - blue bends more than red.
How are both types of abberations corrected in fish?
The fish lens will have different protein layers with different refractive indices which will correct for both chromatic and spherical abberations.
How does a fish focus light?
Change the focus on the retina by moving the lens back and forth.
This is done by a muscle and the suspensory ligament.
The muscle will flex or relax to change focus. The ligament will return it to place after muscular relaxation.
Why does light go through all the cell layers before detection?
If it was too close, couldn't get retinomotor adaptation - functions to protect rods.
What is resolution?
What is sensitivity?
What are both based on?
Resolution means you can tell individual items apart.
Sensitivity means you have a greater ability to sense photons.
Both depend on the photoreceptor-ganglion ratio.
Describe the Pr-Gc ratio as it pertains to good resolution.
Good resolution, can tell items apart, not particularly good in dim light.
Closer to a one to one ratio or PR to GC (PR > GC still)
Describe the Pr-Gc ratio as it pertains to sensitivity.
All the photoreceptor information gets summed into few ganglion cells, so high PR:GC ratio.
Higher summation ratio of photoreceptors to ganglia, need less light.
What fish would have a lower PR:GC ratio?
Fish that need good resolution, lots of bright light available.
What fish would have a higher PR:GC ratio?
Fish that live in turbid environments, more active at night, deeper sea fish.
What are colours due to?
Pigments, achromatic elements and structural colours.
What gets reflected is what?
Where are pigments localized to?
Pigment cells called chromatophores.
Pigments in chromatophores will affect ______ colour.
What are achromatic colours?
Absorb light rather than reflect them.
Different type of pigment that can be synthesized: guanine crystals which reflect all colours and melanin - show black.
What are structural colours?
Light that bounces off of fish scales, bones or skin and arent true pigments.
Green, blue, violet
Rapid or seasonal colour change will be the product of what?
Achromatic and pigments
Which has the longer wavelength, red or blue?
UV light is what wavelength?
below 400nm (blue)
What is the purpose of having UV cones in fish?
To see small zooplankton.
How do we know what cones fish have?
MSP - microscpectrometry
What is MSP?
Take fish eye, place on slide and shine different lights on the cones to determine the absorbance peaks.